Lecture on Aluminium and its Industrial Processing

Importance of Aluminium

• Aluminium and its alloys are crucial metals in everyday life.
  • Resistant to chemicals.
  • Strong yet flexible.
  • Lightweight.

Aluminium Extraction

• Third most common element in Earth's crust.
• Extracted from its oxide via electrolysis.
• Anglesey Aluminium in Holyhead extracts about 135,000 tons/year, half of the UK's total.
• The plant has its own deep water port for importing raw materials.
• Site includes road, rail, and sea shipping facilities.

Plant Infrastructure

• Comprises three plants in one:
  1. Electrolysis
  2. Alloying
  3. Casting

Electrolysis Process

• Takes place in four covered areas, each half a kilometer long.
• Each area contains 78 electrolysis cells.
• Anodes for the process are produced on-site.
• Aluminium oxide (alumina) is stored and fed via underground conveyor belt.
• Alumina imported from Jamaica, Ireland, and Spain.

Pot Lines

• Each pot line contains electrolysis cells operating at 157,000 amps and 4.5 volts.
• Electricity sourced from the National Grid.

Electrolysis Cell Structure

• Steel shell lined with heat-resistant brick and carbon.
• Filled with molten cryolite to dissolve aluminium oxide for conducting electricity.
• 18 carbon anodes dip into the electrolyte.

Electrolysis Chemical Reactions

• Aluminium ions move to the cathode, gain electrons, and become aluminium metal.
• Oxide ions move to the anode, lose electrons, pair up as oxygen molecules.
• Frequent crust breaking to feed new aluminium oxide every 3-4 minutes.

Anode Maintenance

• Anodes burn away gradually, replaced every 28 days.
• Remaining carbon crushed, mixed with coke and pitch, pressed into shape.
• New anodes baked for 24 hours in gas-heated pits.
• Anodes fitted onto steel stubs and electrically connected.

Continuous Operation

• Electrolysis operates 24/7, year-round.
• Power loss over a few hours is catastrophic, causing solidification.

Aluminium Casting

• Liquid aluminium extracted into a brick-lined steel crucible.
• Each cell produces ~50 kg of aluminium per hour.
• Aluminium either cast as pure metal or alloyed (e.g., with magnesium).

Product Forms

• Aluminium cast into various shapes to meet customer needs.

This lecture provides a comprehensive overview of the importance, extraction process, and industrial processing of aluminium, highlighting the role of Anglesey Aluminium in the UK and the technical details involved in the electrolysis and casting processes.